Evidence has been obtained suggesting the presence of acetyl CoA carboxylase and readily dissociable type of fatty acid synthetase in Propionibacterium sheramnii. The demonstration of acetyl CoA carboxylase provides the first evidence for the presence of another biotinyl enzyme in these bacteria in addition to the well-studied biotinyl enzyme, oxaloacetate transcarboxylase. There is a general lack of information on the regulation of lipogenesis in microbial systems. A systematic study is planned to investigate the control of this process at the acetyl CoA carboxylase level. The proposed investigations include: conditions inducing acetyl CoA carboxylase in vivo, role of biotinylation of the apo-enzyme and whether some metabolite (s) could act as an effector of the enzyme. Another objective of this proposal is to isolate and purify acetyl CoA carboxylase and/or its subunits for rigorous characterization. The stipulated studies include: association-dissociation, molecular weight determinations, the mechanism of catalysis and kinetics of the overall reaction as well as of the half reactions, specificity of the subunits in the partial reactions and eventually we will explore whether hybridized enzymes could be formed by substituting subunits of acetyl CoA carboxylase and oxaloacetate transcarboxylase of these bacteria. The results of these investigations should allow us to compare the subunit structure of acetyl CoA carboxylase with acyl CoA carboxylases of diverse origin and with the oxaloacetate transcarboxylase of these bacteria. The results of hybridization studies will hopefully reveal whether there exist homologous regions in these two enzymes.